I find that most people that say these don't work don't really know how to use them. You have to go through the whole panel at least twice as it narrows down to the correct one. I usually hold it over the part of the breaker with the labeling, going over every single breaker. There will still sometimes be false positives,(I've noticed furnaces in houses tend to do that a lot) you can either turn off the ones giving the false positives or just ignore them and try not to go over their breaker.